Conventionally, studies have been carried out on technologies of performing functional thin-film coating or surface processing on the inner surfaces of cylindrical parts such as a valve, a cylinder, a guide bush, a hole in a mold, an endoscope, and a nozzle to obtain corrosion resistance and sliding characteristics superior to those of a base material. A technology of performing surface processing or the like by using non-equilibrium plasma in order to achieve the above object is known in the art. SWP (Surface Wave-excited Plasma) and MVP (Microwave sheath Voltage combination Plasma) are examples of a plasma generation method. The SWP and the MVP have been developed since they have been expected as technologies that increase the plasma concentration and enable surface processing of the inner surface of a small bore of a pipe or the like.
There is a patent document shown below as a technology based on the above MVP. The MVP described in this patent document is plasma that is generated by a microwave introduced along the surface of a metal object when a negative bias voltage is applied to the metal object arranged near microwave introducing means in a chamber. The plasma thus generated distributes along an equipotential surface of the metal object. The microwave is thus propagated along the inner side surface of a pipe or the like, whereby the inner surface can be processed by the generated plasma.
[Patent document 1]    Japanese Patent Application Publication No. JP-A-2004-47207